1. Field of the Invention
This invention relates to a process for drying hydrogen fluoride-carboxylic acid mixtures, i.e., removing water from mixtures of hydrogen fluoride, a carboxylic acid such as acetic acid, and water.
2. Description of Related Art
The following information is disclosed in accordance with the terms of 37 CFR 1.56, 1.97, and 1.98.
Aromatic ketones which can be produced by Friedel-Crafts acylations using hydrogen fluoride as catalyst are possible intermediates for a variety of products having a multiplicity of end uses. Thus, U.S. Pat. No. 4,524,217, issued June 18, 1985 to Davenport et al., discloses a process of using hydroxy aromatic ketones, e.g., 4-hydroxyacetophenone (4-HAP), to make N-acyl-hydroxy aromatic amines, e.g., N-acetyl-para-aminophenol (APAP), better known as acetaminophen, which has wide use as an analgesic. U.S. Pat. No. 4,568,763, issued Feb. 4, 1986 to Davenport et al., discloses the use of hydroxy aromatic ketones such as 4-HAP as an intermediate for the production of N-acyl-acyloxy aromatic amines, e.g., 4-acetoxyacetanilide (4-AAA), which can be used for the preparation of poly (ester-amide)s capable of forming an anisotropic melt phase and suitable for being formed into shaped articles such as moldings, fibers, and films. In addition, 4-AAA may also be hydrolyzed to form APAP. U.S. Pat. No. 4,692,546, issued Sept. 8, 1987 to Davenport, discloses a process wherein hydroxy aromatic ketones, e.g., 4-HAP, are used to produce acyloxy aromatic carboxylic acids, e.g., 4-acetoxybenzoic acid (4-ABA), which is also capable of being used directly to make polymers which can be formed into an anistropic melt suitable for the formation of shaped articles. Moreover, 4-ABA can be hydrolyzed to 4-hydroxybenzoic acid (4-HBA) which can be used as an intermediate for the production of preservatives, dyes, and fungicides. Pending U.S. patent application Ser. Nos. 661,552, filed Oct. 17, 1984 by Gerberich, and 689,533, filed Jan. 7, 1985 by Hilton, disclose processes wherein hydroxy aromatic ketones, e.g., 4-HAP, are used as intermediates for the production of aromatic diols, e.g., hydroquinone, which has utility as a photographic developer, polymerization inhibitor, dye intermediate, and anti-oxidant.
The foregoing U.S. patents and pending applications each shows the production of aromatic ketones by the Friedel-Crafts acylation of aromatic compounds with a carboxylic acid using hydrogen fluoride as catalyst. In addition to these disclosures, pending applications Ser. Nos. 716,016, filed Mar. 26, 1985 by Mott et al., and 106,940, filed Oct. 8, 1987 by Davenport et al., teach processes for the production of 4-HAP by the Friedel-Crafts acetylation of phenol with acetic acid utilizing hydrogen fluoride as catalyst and reaction conditions within certain prescribed ranges.
The following published patents and literature articles as well as pending U.S. patent applications also teach processes utilizing hydrogen fluoride in the production of aromatic ketones by the Friedel-Crafts acylation of aromatic compounds using a carboxylic acid such as acetic as acylating agent:
U.S. Pat. No. 4,593,125, issued June 3, 1986 to Davenport et al., shows the acylation of various substituted naphthalenes using hydrogen fluoride as catalyst to obtain the corresponding substituted naphthones, e.g., 6-hydroxy-2-acetonaphthone (6,2-HAN).
Dann et al. in a dissertation included as part of a series of Reports from the Institute for Applied Chemistry of the University of Erlangen, received for publication on Jan. 7, 1954 and published in Annalen der Chemie 587 Band, pages 1 to 15, disclose the acetylation of guaicol with acetic acid to produce a mixture of 4-hydroxy-3-methoxyacetophenone and 3-hydroxy-4-methoxyacetophenone, and the acetylation of phenol with acetic acid to produce 4-HAP, all in the presence of hydrogen fluoride as catalyst.
Simons et al., Journal of the American Chemical Society, 61, 1795 and 1796 (1939), teach the acylation of aromatic compounds using hydrogen fluoride as a condensing agent and in Table 1 on page 1796 show the acetylation of toluene with acetic acid to product p-methylacetophenone, the reaction of toluene and valeric acid to produce p-tolyl n-butyl ketone, and the reaction of toluene with benzoic acid to produce p-tolyl phenyl ketone, as well as the acetylation of phenol with acetic acid to produce 4-HAP.
Pending application Ser. No. 158,141 filed Mar. 4, 1988 by Elango et al., shows the production of 4'-isobutylacetophenone by the Friedel-Crafts acetylation of isobutylbenzene with an acetylating agent which may be acetic acid, using a catalyst which may be hydrogen fluoride. The 4'-isobutylacetophenone is disclosed as an intermediate in a process for the production of ibuprofen.
Other references of interest are as follows:
Kelley, U.S. Pat. No. 2,388,156, issued Oct. 30, 1945, discloses the removal of water from an azeotropic mixture of hydrogen fluoride and water by contracting the mixture with a liquid hydrocarbon solution containing a relatively water-insoluble organic nitrogen base to form an organic hydrofluoride which is more soluble in the hydrocarbon than in water. The hydrocarbon solution of hydrofluoride is then heated to liberate hydrogen fluoride which is recovered.
Cohen, European Patent Publication No. 71,293, published Feb. 9, 1983, teaches the separation of carboxylic acids from mixtures with non-acids such as water by extraction with a lower lactam such as N-methyl-2-pyrrolidone.
Other references cited by Cohen and showing the use of organic bases to separate carboxylic acids from non-acids such as water, are U.S. Pat. No. 3,878,241 (1,2-dimorpholinoethane); DE-A 2,408,011 (N-methylacetamide); DE-A 2,545,730 (N-formyl morpholine); U.S. Pat. No. 3,478,093 (lactams immiscible with mixture to be separated); and DE-A 2,545,658 (secondary amides).
In general, processes for producing aromatic ketones by acylating an aromatic compound with a carboxylic acid utilizing hydrogen fluoride as a catalyst employ an excess of hydrogen fluoride and carboxylic acid and result in a product mixture comprising hydrogen fluoride, water and carboxylic acid as well as aromatic ketone product, which mixture must be purified both to obtain aromatic ketone of sufficient purity to make it suitable for further use, and to recover the hydrogen fluoride and carboxylic acid for recycling to the process.
One method of purification includes an initial solvent-assisted distillation of the mixture as disclosed, for example, in U.S. Pat. No. 4,663,485, issued May 5, 1987 to Murphy et al., and pending application Ser. No. 013,311 filed Feb. 11, 1987 by Murphy et al. In this method, a composition comprising an aromatic ketone, e.g., 4-hydroxyacetophenone (4-HAP), and an inorganic fluoride consisting essentially of hydrogen fluoride (HF), is distilled in a column or other vessel in the presence of an assisting solvent which is stable in the presence of HF. The vapor overhead comprises a major portion of the HF in the feed to the distillation vessel mixed with some assisting solvent. A liquid residue containing solvent and most of the aromatic ketone in the feed and which may contain heavy ends other than the desired aromatic ketone, is obtained from the base of the column. When the composition being purified is that resulting from the acylation of an aromatic compound with a free carboxylic acid using HF as a catalyst, and thus contains water and carboxylic acid as well as aromatic ketone and HF, then the overhead in the solvent-assisted distillation column will contain water and some carboxylic acid as well as HF and the assisting solvent. After separation of the assisting solvent by decantation or distillation (assuming the assisting solvent is not the carboxylic acid) the composition remaining will comprise HF, carboxylic acid and water, with possibly a small amount of assisting solvent. However, before recycling HF and carboxylic acid to the process (a step necessary for economic reasons), the water must be removed or substantially reduced in content since its presence inhibits the acylation reaction due to equilibrium considerations.
Although the vapor pressures of the pure components may indicate that a water-HF-carboxylic acid mixture should be easily separated, azeotropes and the non-idealities often make the separation difficult. For example, HF forms a high-boiling azeotrope with both water and various carboxylic acids such as acetic. While water and a carboxylic acid such as acetic do not form an azeotrope, their relative volatilities are lower than ideal solution laws predict.